Motor fuel



3,021,205 MOTOR FUEL Harry Chafetz, Pougnkeepsie, and George W. Eckert, Wappingers Falls, N.Y., assignors to Texaco Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 1, 1960, Ser. No. 11,980 Claims. (Cl. 44-66) This invention relates to hydrocarbon fuel compositions of high octane rating. More specifically, it involves the discovery that the octane rating of leaded gasoline fuels of prescribed composition is substantially improved by the addition thereto of acyloxy nitriles.

The recent increases in compression ratios of automobile engines have placed a severe strain on petroleum refiners to produce fuels having the octane ratings demanded by these engines. Premium fuels at the present time have research octane ratings between 97 and 101 and it has been predicted that premium fuels will have to have octane ratings between 105 and 110 five years from now in order to satisfy the octane requirements of the high compression automotive engines predicted for that date.

In order to produce premium fuels of octane ratings of 95 and above, it has been necessary for refiners to rely heavily on catalytic refining operations such as fluid catalytic cracking, catalytic reforming, alkylation and catalytic isomerization.

Catalytic cracking and catalytic reforming, which are the most widely used refining operations in the production of high octane fuels, produce substantial quantities of aromatics; catalytic cracking also produces a substantial amount of olefins. It is well known that olefins and aromatics, although possessing high octane ratings, have a poorer response to organo-lead compounds such as tetraethyl lead than saturated aliphatic gasoline components. Accordingly, as the aromatic and olefinic content of the gasolines have increased to meet the octane levels required by modern automotive high compression engines, the lead response of the resulting fuels has diminished. Stated another way, the octane increment obtainable by the addition of an organo-lead compound decreases as the aromatic and olefin contents of the base fuel increase. The subject invention involves the discovery that the octane rating of leaded motor fuels containing a substantial concentration of high octane components, that is, aromatic, olefins and mixtures thereof, is markedly improved by the addition of a small amount of acyloxy nitriles of prescribed composition.

In a commonly-assigned copending application, Serial No. 689,466, filed October 2, 1958, by G. W. Eckert, it is disclosed that hydrocarbyl monocarboxylic acids substantially raise the octane rating of a motor fuel containing an organo-lead anti-knock agent and a substantial concentration of high octane components which may be aromatic hydrocarbons, olefinic hydrocarbons or mixtures thereof. In a series of cases filed subsequent to the afore-identified copending application it is disclosed that a number of monocarboxylic acid derivatives such as their tertiary alkyl esters which are converted to hydrocarbyl monocarboxylic acids during combustion are also effective octane appreciators for leaded fuels of prescribed composition. The subject invention involves the discovery that certain acyloxy-substituted nitriles are effective octane appreciators for leaded motor fuel compositions having the prescribed aromatic and/or olefin content.

The high octane hydrocarbon motor fuel of this invention comprises high octane components including a substantial concentration of aromatic hydrocarbons, olefinic hydrocarbons and mixtures thereof, an organo-lead antiknock agent and an acyloxy nitrile wherein the acyloxy radical is substituted either on the carbon atom contain- BJBZLZQS Patented Feb. 13, 1962 ing the nitrile radical or on a carbon atom adjacent to the nitrile-containing carbon atom. The acyloxy nitriles are present in leaded fuels in concentrations between 0.1 and 5.0 and preferably between 0.2 and 2.0 volume percent.

The action of acyloxy nitriles in appreciating the octane rating of gasoline is characterized by several unusual features. In the first instance, these compounds are ineffective in raising the octane rating of gasoline unless an organo-lead anti-knock agent, normally tetraethyl lead, TEL, is a component of the gasoline mixture. The second unusual characteristic of their action in appreciating the octane rating of gasolines is the fact that an equivalent concentration of acyloxy nitrile causes a greater octane improvement above the 100 octane level than below the 100' octane level. The third unusual feature of the action of acyloxy nitriles is that they appear to have substantially little effect on the octane rating of a gasoline consisting essentially of saturated aliphatic hydrocarbons even though an organo-lead anti-knock agent is present.

Since organo-lead anti-knock agents exert their greatest octane appreciation in predominantly saturated paraffinic base hydrocarbon gasolines and have the least effect on the octane rating of aromatic and olefin-rich gasolines, the present invention neatly complements tetraethyl lead as an octane improver. Acyloxy-substituted nitriles have their minimum eifect where tetraethyl lead has its maximum effect and exert their maximum effect on octane values where tetraethyl lead has its minimum effect- The novel f-uel compositions of this invention have a minimum concentration of aromatic and/or olefin components ofat least 5 volume percent. The aromatic and/ or olefin components of the motor fuel of the invention can constitute as high as 100 volume percent thereof but usually comprise between 20 and 80 volume percent.

A 5 percent concentration of aromatics and/ or olefins appears to be necessary for acyloxy nitriles to exert a significant octane improvement.

The aromatic components of the motor fuel of the invention are generally supplied by catalytic reforming or catalytic cracking, operations. Catalytic reformate is particularly high in aromatics. The olefin components of the motor fuel of the invention are derived from thermal cracking, catalytic cracking or polymerization.

The organo-lead reagent necessary for the action of acyloxy nitriles as octane improvers is usually a tetraalkyl lead compound. Tetraethyl lead is universally used as an anti-knock agent but other tetraalkyl lead compounds such as tetramethyl lead, tetrabutyl lead, tetraamyl lead, tetrapropyl lead, etc., possess anti-knock properties and are used in the fuel compositions of the invention in conjunction with acyloxy nitriles.

The tetraethyl lead mixtures commercially available for automotive use contain an ethylene chloride-ethylene bromide mixture as a scavenger for removing lead from the combustion chamber in the form of volatile lead halides. Tetraethyl lead fluid, the commercial product, comprises tetraethyl lead, ethylene chloride and ethylene bromide, the latter two reagents being present in 1.0 theory and 0.5 theory, respectively, theory denoting the stoichiometric amount required for reaction with the lead content of the tetraethyl lead.

The organo-lead reagent is present in the fuel compositions of the invention in concentration between 0.5 ml. per gallon up to the statutory limit of organo-lead reagent concentration which, at the present time, is 4- ml. per gallon in thev case of automotive fuel and 4.6' ml. per gallon in the case of aviation fuel. The usual concentration of tetraethyl lead is between 1 and 3 ml. per galtained with acyloxy nitriles at TEL concentrations of 6 ml. per gallon and higher.

The acyloxy nitriles which are effective in increasing the octane rating of leaded gasolines containing the prescribed aromatic and/or olefin content have the acyloxy radical attached either to the carbon atom substituted with the nitrile radical or on the carbon atom adjacent thereto. Acyloxy nitriles containing the acyloxy radical and the nitrile radical on the same carbon atom appear to be more eflective than compounds containing the acyloxy and nitrile radicals on adjacent carbon atoms. The eifective acyloxy nitriles have the following general formula:

RI! RCOO J) (CH2) nCN in which R is a C to C hydrocarbyl radical, R is a hydrogen atom or a hydrocarbyl radical containing 1-8 carbon atoms, R" is a hydrogen atom, a hydrocarbyl radical containing l-8 carbon atoms, or a C to C hydrocarbyl radical substituted with a COOR' in which said R is a C to C aliphatic hydrocarbyl radical, and n has a value of or 1. In the above formula, R is advantageously a C to C aliphatic hydrocarbyl radical, R is advantageously a hydrogen atom or a C to C aliphatic hydrocarbyl radical and R" is advantageously a hydrogen atom, a C to C aliphatic hydrocarbyl radical or a C to C aliphatic hydrocarbyl radical containing a COOR in which R' is C to C aliphatic hydrocarbyl radical.

Acyloxy nitriles which are effective as octane appreciators are formed by esterification of cyanohydrins in which the hydroxyl radical and the cyanohydrin radical are on the same or adjacent carbon atoms. Examples of effective acyloxy nitriles are the following: Ethylene cyanohydrin acetate, acetone cyanohydrin acetate, 3-cyano 3 acetoxyethylbutyrate, 2-cyano-2-acetoxybutane, 2 cyano-2-propionoxybutane, 2-cyano-3-acetoxypentane, 3-cyano 3 butyroxypentane, 3-cyano-3-caproxyhexane, 3-cyano-3-propionoxyhexane and acetone cyanohydrin benzoate.

The acyloxy nitriles must be present in the leaded aromatic and/or olefin-containing compositions of the invention in a minimum concentration of 0.1 volume percent before a significant octane appreciation is realized. When the concentration of the acyloxy nitrile is below 0.1 volume percent, there is no noticeable octane improvement in leaded gasolines of prescribed composition. The preferred concentration of acyloxy nitrile falls between 0.2 and 2.0 volume percent with maximum octane appreciation generally being obtained at concentrations between 0.5 and 1.5 volume percent. Although concentrations of acyloxy nitrile as high as 5 volume percent may be employed, economic considerations preclude the use of such high concentrations. In addition, there is a significant decrease in octane appreciating action after the acyloxy nitrile concentration exceeds about 2.0 volume percent.

In Table I there is shown the efiectiveness of the acyloxy nitriles of prescribed composition in raising the octane rating of a leaded fuel composition containing the prescribed aromatic and/or olefin content. The base fuel employed in Table I had a research octane number (RON) of 105, a motor octane number (MON) of 97.8 and comprised approximately 8 volume percent n-butane, 40 percent isobutylene-isobutane alkylate, 12 percent light fluid catalytically cracked naphtha and 40 percent heavy platformate; the base fuel contained 3 cc. of TEL per gallon. Fluorescent indicator analysis (PIA) of the 105 octane base fuel indicated an aromatic content of approximately 35 percent and an olefin content of approximately 6 percent.

The data in the above table show the effectiveness of acyloxy nitriles of prescribed formula in appreciating the octane rating of leaded fuels containing at least 5% of aromatics and/or olefins. It is noted that the compounds wherein the acyloxy radical is attached to a car bon atom containing the nitrile radical, namely the ace tate of acetone cyanohydrin and 3 cyano 3 acetoxybutyrate, are more effective than the compounds wherein the acyloxy radical is one carbon removed from the carbon atom containing the cyano radical, namely, the acetate of ethylene cyanohydrin. The greater eliectiveness of the compounds wherein the acyloxy radical and the nitrile radical are in the same carbon atom is attributed to the fact that such compounds decompose more readily to give a monocarboxylic acid moiety in the fuel during its combustion.

In Table II there is shown the octane appreciating action of acyloxy nitriles in a commercial premium motor fuel having the same hydrocarbon components as that employed in Table I, but containing 4 cc. of TEL per gallon. The fuel employed in Table II containing 4 cc. of TEL per gallon had an RON of 106.5 and an MON of 100.1.

The data in Table II demonstrate the effectiveness of acyloxy nitriles of prescribed composition in improving the octane ratings of a leaded fuel containing 4 cc. TEL per gallon.

In Table III there is shown the octane appreciating action of acyloxy nitriles in a commercial premium motor fuel having an RON of 100.3 and an MON of 89.2. The premium motor fuel employed in Table II contains 3 cc. of TEL per gallon and had an IBP of 89 F. and an end point of 372 F. FIA indicated that it comprised 53% saturated hydrocarbons, 38% aromatics and 9% olefinic hydrocarbons.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and,

therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A hydrocarbon fuel in the gasoline boiling range containing an organo-lead anti-knock agent, high octane components selected from the group consisting of olefinic hydrocarbons, aromatic hydrocarbons and mixtures thereof in a concentration of at least 5.0 volume percent of said fuel, and an acyloxy nitrile having the general formula in which R is a C C hydrocarbyl radical, R is selected from the group consisting of a hydrogen atom and a hydrocarbyl radical containing 1-8 carbon atoms, R" is selected from the group consisting of a hydrogen atom, a hydrocarbyl radical containing 1-8 carbon atoms and a C -C hydrocarbyl radical substituted with a C00 in which said R is a C -C aliphatic hydrocarbyl radical and n has a value selected from the group consisting of 0 and 1, said acyloxy nitrile being present in a concentration between 0.1 and 5.0 volume percent, said concentration being sufiicient to effect substantial octane appreciation of said leaded fuel.

2. The hydrocarbon fuel according to claim 1 in which said organo-lead anti-knock agent is present in a concentration between 0.5 and 4.6 cc. per gallon.

3. The hydrocarbon fuel according to claim 1 in which said acyloxy nitrile is present in a concentration between 0.2 and 2.0 volume percent.

4. A hydrocarbon fuel in the gasoline boiling range containing an alkyl lead anti-knock agent in a concentration of at least 0.5 cc. per gallon, high octane components selected from the group consisting of olefinic hydrocarbons, aromatic hydrocarbons and mixtures thereof in a concentration of at least 5.0 volume percent and an acyloxy nitrile of the general formula:

RI! RCOO+(OH2)BCN wherein R is a C -C aliphatic hydrocarbyl radical, R

is selected from the group consisting of hydrogen and a C -C aliphatic hydrocarbyl radical and R" is selected from the group consisting of hydrogen, a C -C aliphatic hydrocarbyl radical and a C to C aliphatic hydrocarbyl radical containing a COOR radical in which R is a C to C aliphatic hydrocarbyl radical and n has a value selected from the group consisting of 0 and 1, said acyioxy nitrile being present in a concentration between 0.1 and 5.0 volume percent, said concentration being sufiicient to effect substantial octane appreciation of said leaded fuel.

5. The hydrocarbon fuel according to claim 4 in which said acyloxy nitrile is present in a concentration between 0.2 and 2.0 volume percent.

6. The hydrocarbon fuel according to claim 4 in which said high octane components constitute 2080 volume percent of said fuel.

7. The hydrocarbon fuel according to claim 4 containing 1.0 to 4.6 cc. TEL per gallon.

8. The hydrocarbon fuel according to claim 4 in which said acyloxy nitrile is ethylene cyanohydrin acetate.

9. The hydrocarbon fuel according to claim 4 in which said acyloxy nitrile is acetone cyanohydrin acetate.

10. The hydrocarbon fuel according to claim 4 in which said acyloxy nitrile is 3-cyano-3-acetoxy ethyl butyrate.

References Cited in the file of this patent UNITED STATES PATENTS 2,135,327 Conquest Nov. 1, 1938 2,210,942 Lipkin Aug. 13, 1940 2,887,368 Buckrnann May 19, 1959 2,905,679 Brockman et a1. Sept. 22, 1959 FOREIGN PATENTS 837,965 France Nov. 28, 1938 72/1958 Trinidad and Tobago Oct. 9, 1958 OTHER REFERENCES Improved Motor Fuel Through Selective Blendings, by Wagner et al., paper presented before the 22nd annual meeting of the American Petroleum Institute, Nov. 7, 1941, pages -89. 

1. A HYDROCARBON FUEL IN THE GASOLINE BOILING RANGE CONTAINING AN ORGANO-LEAD ANIT-KNOCK AGENT, HIGH OCTANE COMPONENTS SELECTED FROM THE GROUPCONSISTING OF OLEFINIC HYDROCARBONS, AROMATIC HYDROCARBONS AND MIXTURES THEREOF IN A CONCENTRATION OF AT LEAST 5.0 VOLUME PERCENT OF FUEL, AND AN ACYLOXY NITIRLE HAVING THE GENERAL FORMULA 